EFFICIENCY ANALYSIS OF THE USE OF HIGHLY GRAPHITIZED
BOTTOM BLOCKS IN 156 – 160 kA ALUMINUM ELECTROLYZERS
O. Yu. Urazlina,
V. I. Churilin,
E. N. Panov,
G. N. Vasil’chenko,
and A. Ya. Karvatskii
Translated from Novye Ogneupory, No. 12, pp. 27 – 32, December, 2004.
Original article submitted June 22, 2004.
A comprehensive efficiency analysis of the energy consumption is carried out for two types of aluminum
electrolyzers using graphitized bottom blocks available from the Ukrainian Graphite JSC. The use of bottom
blocks high in graphite (50 and 70%) leads to economic consumption of electric power, increased output, and
extended service life of the electrolyzers.
A challenge in the world aluminum industry is reduction
of the specific consumption of electric energy, increase in
the unit power of electrolyzers, and extension of their ser-
Specific consumption of electric energy is an important
characteristic of the energy efficiency of an aluminum
electrolyzer. The specific consumption is a function of the
electrolysis process parameters such as current efficiency
and working voltage of the electrolyzer. Part of this voltage
is spent usefully on heating, dissolution, electrochemical de-
composition of alumina etc., whereas the other part (about
50%) is dissipated into the environment as heat losses.
Therefore an issue of major concern in the aluminum elec
trolysis is the decrease in working voltage and, consequently,
reduction of heat losses. The specific consumption of electric
energy can be decreased by increasing the current efficiency
and by decreasing the working voltage. The working voltage
can be economically decreased using: (i) proper refractory
materials (for example, bottom or cathode blocks with a high
concentration of graphite) and heat insulators for the cathode
unit; (ii) automatically controlled feed of alumina; (iii) auto
matically controlled interelectrode spacing (IES), or (iv)
electrolyte composition variation. Most economical in the
production of aluminum are electrolyzers operating at low
working voltage, high current efficiency, and high current
As is known, increasing the concentration of graphite
improves strength characteristics, resistance to corrosive at
tack of molten media, heat conductivity, and electric resisti
vity of cathode blocks . However, despite these advan-
tages, the replacement of amorphous blocks by graphitized
blocks may incur damage to the refractory lining — for ex-
ample, the early leakage in the bottom lining, increased scull
buildup, and, as a consequence, decreased current efficiency,
etc. To obtain a positive effect from this replacement, judi-
cious design of the cathode lining and properly controlled
operating parameters of the electrolyzer are needed.
Using bottom blocks high in graphite causes a voltage
drop, which makes it possible to increase the current strength
on condition that the cathode lining has been modified pro
perly. The decreased concentration of metal and increased
current strength make it possible to optimize the workspace
configuration (WSC), in particular, to decrease slag scull
buildup in the anode compartment. In turn, this leads to the
increase in current efficiency owing to the decrease in hori
zontal current components.
Thus, a comprehensive approach makes it possible to im
plement modernization of the aluminum productions in all
aforementioned aspects, namely, reduction of the specific
consumption of energy, increasing the output, and extending
the service life of the electrolyzer.
A scheme for evaluating the efficiency of cathode blocks
high in graphite should involve the following steps:
– choice of the base types (prototypes) of electrolyzers
intended for use of graphitized bottom blocks;
– survey of technical documentation, performance pa
rameters, and experimental data (temperature regimes for
cathode casings, workspace configuration, etc.) on the proto
– development of the refractory lining for cathodes;
Refractories and Industrial Ceramics Vol. 46, No. 2, 2005
1083-4877/05/4602-0093 © 2005 Springer Science+Business Media, Inc.
Ukrainian Graphite Joint-Stock Co., Zaporozhe, Ukraine; Na
tional Technical University of Ukraine, Kiev, Ukraine.